The subject technology includes membrane-based devices for multi-step assays that include fluid storage zones intended to enable the automated sequential delivery of reagents, which are pre-dried on the device, to a test zone preferably from a single addition of fluid to the device. These devices may be useful for performing multi-step assays automatically without requiring any input from the user after the initial sample is added to the device. In some aspects, multiple additions of fluid to the device may be used.